Conformational studies on histone H3 and its CNBr peptides

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Histone H3 plays a crucial role in DNA packaging and gene regulation.
• Understanding histone conformational dynamics is key to elucidating chromatin structure and function.

Purpose of the Study:

• To investigate the salt-induced conformational changes of histone H3 and its specific peptides.
• To determine the role of different histone H3 peptide segments in structural transitions and aggregation.

Main Methods:

• Preparation and purification of histone H3 and various H3 peptides (1-120, 1-90, 91-135, 91-120, 121-135).
• Circular dichroism (CD) spectroscopy, including near-ultraviolet CD, to analyze secondary and tertiary structural changes.
• Ionic strength manipulation to induce and observe conformational transitions and aggregation.

Main Results:

• Reduced histone H3 and peptides 1-120, 91-135, and 91-120 showed biphasic formation of alpha-helix and beta structures upon salt increase.
• Peptide 1-90 exhibited monophasic formation of alpha-helix and beta structures, while peptide 121-135 remained unfolded.
• Most peptides, except 121-135, aggregated at higher ionic strengths.
• Near-UV CD spectra of histone H3 and peptide 1-90 were highly similar, indicating conserved conformational changes.

Conclusions:

• Histone H3 undergoes significant salt-induced conformational changes, involving alpha-helix and beta structure formation.
• Peptide 1-90 appears to represent key structural elements responsible for the conformational behavior of intact histone H3.
• The findings support a model where histone H3 segments initially self-associate in parallel, leading to larger aggregate formation.